1. Field of the Invention
The present invention relates to a buckle device which structures a seat belt device of a vehicle and which is for holding a tongue plate attached to a webbing belt.
2. Description of the Related Art
One longitudinal direction end of a webbing belt, which structures a seat belt device for restraining the body of a vehicle occupant seated in a seat of a vehicle, is anchored on a take-up shaft of a take-up device which is provided, for example, at the side of the seat. The other end of the webbing belt is fixed to an anchor plate which is provided in a vicinity of the take-up device. Moreover, the longitudinal direction intermediate portion of the webbing belt passes through a through-hole of a through anchor which is provided above the take-up device (e.g., at the upper end side of the center pillar of the vehicle), and is folded over backward downwardly.
The portion of the webbing belt between the folded-over portion at the through anchor and the other end passes through a through-hole formed in a tongue plate. By pulling the tongue plate, the webbing belt, which is taken-up on the take-up shaft of the take-up device, is pulled out. The webbing belt is set in a state of being applied to a vehicle occupant by, in the state in which the webbing belt is pulled-out, inserting the tongue plate in and connecting the tongue plate to a buckle device which is provided at the side of the seat opposite the side at which the take-up device is provided.
Moreover, an ejector is provided at the buckle device on the locus of movement of the tongue plate within the buckle device. The ejector is urged in the direction opposite to the direction of insertion of the tongue plate into the buckle device, by an urging mechanism such as a compression coil spring or the like. When the tongue plate is inserted in the buckle device, the ejector is pushed by the tongue plate and moves against the urging force of the urging mechanism. When the mechanical connection between the buckle device and the tongue plate is released in order to cancel the applied state of the webbing belt, the urging mechanism pushes the tongue plate by the urging force of the urging mechanism and via the ejector, so as to make the tongue plate come out from the buckle device.
There are buckle devices having a structure which is provided with a so-called “buckle switch” (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 2001-157603).
The buckle device, which is provided with the buckle switch and is disclosed in the aforementioned document, is equipped with a lock pin which interlocks with a latch. The buckle device has a magnet which interlocks with the lock pin. Fluctuations in a magnetic field due to movement of the magnet which is interlocked with movement of the lock pin at the time when the latch moves to a position of engaging with the tongue plate, are detected by a Hall element. On the basis of the results of detection, for example, a warning light provided at the instrument panel of the vehicle is lit so that the vehicle occupant is urged to apply his/her webbing belt.
The above-described buckle switch is a structure which detects that the tongue plate, which is inserted in the buckle device, has pushed the ejector and the latch has moved. Thus, even if some external force is applied to the latch or another member such that the latch moves even though the tongue plate has not been inserted, the buckle switch will carry out the same output as in the case in which the latch engages with the tongue plate.
Namely, buckle switches heretofore cannot detect whether or not the latch is actually engaged with the tongue plate. Therefore, it cannot be said that attachment of the tongue plate to the buckle device is detected, and there is still room for improvement. A buckle device having a mechanism which can reliably detect the attachment of the tongue plate is desired.